I see them as cinema's answer to the Ronseal commercial, reassuring potential customers that a film does exactly what it says on the tin. Consumer advice notices were first added to movie posters by distributors and the British Board of Film Classification (BBFC) in 1997 and, waiting on tube and railway platforms, I've stood in front of hundreds of them, becoming fascinated by the quirks of their banal vocabulary.

Their laudable role, outlined on the BBFC website, is to make cinema-goers, particularly parents, aware of "any potentially disturbing subject matter and the frequency and intensity of key issues of language, sex/nudity and violence".

The advisory for John Travolta's 12A-rated American firefighter drama Ladder 49 tells you that it "contains one use of strong language and moderate peril", and I adore the slightly archaic wording of the latter ingredient, which conjures up some stiff upper-lipped officer warning his troops to expect "a spot of moderate peril" at the Somme. James Cameron's Titanic picked up a 12 certificate for "nudity, language, threat and violence"; "threat" on this occasion meaning "hundreds of liner passengers menaced by giant iceberg".

Some films earn a unique advisory, for example Harry Potter and the Chamber of Secrets, with its "mild language and horror, and fantasy spiders". Not long ago Team America: World Police became the first - let's hope the last - picture advertised with a promise of "puppet sex".

This directness has even won over marketing experts. The team at Pathé, promoting the January release of tube-train horror flick Creep, devised TV commercials that simply flashed up the BBFC advisory one word at a time: "Contains. Strong. Bloody. Violence." Gore enthusiasts enticed; job done. As with medicine, it seems, so with movies: always read the label.